Train-despatchers telephone-circuit.



H. 0'. BGBRTON.

- TRAIN DESPATGHBR'S TELEPHONE CIRCUIT.

V APPLICATION-FILED MAY17, 1912.

1 9 1 1 19 1 3 Patented Sept. 15, 19M.

W/imsses I in mniar:

'. A HQWy-CTZT 'QF/"0m "pr-nan stares rarnn' men.

HENRY C. EG-ERTON, OF PASSAIG, NEW JERSEY, ASSIGNOR. 'IO WESTERN ELECTRIC COMPANY, OF NEW Y01EtK, N. Y., A CORPORATION OF ILLINOIS.

TEAIN-DESPATCHERS TELEIHONE-CIRCUIT.

To all whom. it may concern Be it known that I, HENRY C. EGERTON, citizen of the- United States, residing at Passaic, in the county of Passaic and State of New Jersey, have invented a certain new and useful Improvement in Train-Despatchcrs TelephoneCircuits, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone stations, and the object is to provide apparatus for controlling the use of two kinds of tele phone receivers of different characteristics.

According to this invention, one of the receivers which may be of the loud speaking type and of high resistance is adapted by means of a switch, when in one position, to be connected in parallel with the secondary winding of an induction coil, this switch in the alternate position connecting the second receiver which may be an ordinary head telephone and of low resistance in series with the secondary winding. A second switch is preferably provided whereby the primary and secondary windings of the induction coil may be either switched out of circuit or placed in operative condition, this switch being capable of use in the same mam ner whether the loud speaking or head receiver is for the moment connected in circuit by the first mentioned switch.

One advantage of this invention is that the user who, for example, may be a train despatcher has the choice of two receiving instruments, one of which, the loud speaking instrument, may be normally left in service and does not require his presence in the immediate vicinity of the instrument, the other being the highly eiiicient head receiver, which he can make use of at times when it is desirable that he give close attention to the telephone, and in cases when the quality of transmission over the line is low.

The drawing is a diagram of the circuit and apparatus connections.

The two limbs of the telephone circuit are shown at 1 and 2; a condenser 0 may be included in one'limb, as in 1. The transmitter 'w is in a local circuit including battery 03, primary 3) of an induction coil, and contacts 30 and g of a switch 5, having movable contacts g and 2', and fixed contacts 30, 31 and 32; contacts 9- and are operated by separat- Specification of Letters Patent. Application filed may 17, 1912. Serial No. 697,905.

Patented Sept. 15, 119114 ing them. This may be done by the use of a foot treadle or in any other manner well known; There are two main line branches as and y. Branch m includes the secondary coil 8, head telephone h and contacts 22 and f of a switch a. This switch ahas fixed contacts 20, 21, 22 and 23, and movable contacts .6 and f operated by a depressible key which may be locked down and released, in wellknown manner. The resistance of the coil of telephone h is low which may be about 70 ohms. In the second main line branch there is included a loud speaking telephone t having a high resistance which may be about 600 ohms; it is provided with a trumpet 0 about eighteen inches or two feet inlength so that the ear of the listener may be considerably removed from the diaphragm. In branch 3 is also included contacts e and 20 of switch a. A. shunt circuit is formed around secondary coil 8, and in this shunt there are two contacts in series, one controlled by each switch a and 6. Contacts e and 21 are operated by switch a, and

contacts 2' and 31 by switch 5. The shunt circuit may be traced from 1 via g 21, 40, 31, 2', 41, to Q9. A break point 7, 22, of switch a operates to make and break branch :0, and a contact 2', 32 of switch I), operates to make and break a by-path of branch at either when circuit is made at f, 22, or is made at f, 23. A branch conductor containing a resistance 33 of say, 20 ohms, connects main conductor 2 with contact 23 of switch a, and when switch 6 is shifted contact 2' engages contact 32 so that telephone h is in a branch from 1 via 8, w, h, 22, f, 2, and a parallel branch is completed via 2, 33, 23, 32, 2', 41, and w. This decreases the transmission loss, due to connecting telephone h in series with coil 8, it also reduces the side tone in receiver 72..

It results from the construction shown and described that the despatcher may alternately use the head telephone h and the loud speaking telephone t, operating the switch a to bring one or the other into operation, and he may operate the switch I) to bring the transmitter and induction coil into use whether the receiver t or 72. is for, the

moment in service. The actuation of switch 5 will connect, in one case, the secondary winding 8 in parallel with the receiver t and, in the other case, this winding in series with the receiver h. In the the resistance 33.

What I claim is:

1. In a telephone station, line conductors,-

a transmitter and primary winding of an induction coil, a secondary winding for said induction coil, a and a low impedance receiver, means for placing either said high impedance or said low impedance receiver in circuit across said line conductors, and means for connecting said secondary winding in series with said low impedance receiver or in parallel with said high impedance receiver.

2. In a telephone circuit of the character described, line conductors, a local transmitter circuit including a transmitter, battery, and the primary winding of an induction'c'oil, a secondary winding for said in duction 0011, a

high impedance receiver, a

low impedance receiver, means for placing either said high impedance or said low impedance receiver 1n circuit across said line conductors, and means for placing said secondary Winding either in series with said low impedance receiver or in parallel with said high impedance receiver and simultaneously closing said local transmitter circuit.

In a telephone circuit of the character described, line conductors, a local transmitter circuit including a transmitter, battery,

latter case the re ceiver it will at the samet'ime be shunted by high impedance receiver and the primary winding of an induction coil, a secondary winding for said induction coil, a high impedance receiver, a low impedancereceiver, a switch for placing either said high impedance receiver or said low impedance receiver in circuit across said line conductors, and a] second switch for operatively connecting said secondary winding in series with said low impedance receiver or in parallel with said-high impedance reclose a break point in the first branch, break said shunt circuit at a second point, and close the local circuit.

In witness whereof, I, hereunto subscribe my name this 16th day of May A. 1)., 1912.

HENRY C. EGERTON. Witnesses O. D. M. GUTHE, WALTER F. HOFFMAN. 

